The present invention relates generally to roll testing automotive vehicles, and more particularly, to a tilting platform.
Designers of automotive vehicles find it necessary to conduct numerous tests on proposed vehicle designs before a new vehicle can be sold to consumers. Many of these tests are mandated by government regulations, but many additional tests are also conducted voluntarily by vehicle designers. The types of tests that designers conduct on proposed vehicle designs are directed to a number of potential concerns. Thus, some tests are directed to the performance and customer acceptance of the new vehicle, while other tests focus on safe operation of the vehicle.
One test that is commonly conducted on automotive vehicles is referred to generally as roll testing. Roll stability is a critical factor when designing new vehicles because roll stability affects safety, handling performance, and driver comfort and satisfaction. Roll stability of a completely assembled vehicle, however, is difficult to calculate theoretically because each individual part in a vehicle works together to affect overall roll stability. Therefore, laboratory tests are usually performed on a sample vehicle to determine the roll characteristics of the new vehicle design. Typically, this laboratory test is performed by supporting the weight of the vehicle at the vehicle tires and slowly rotating the entire vehicle around a longitudinal axis that extends from the rear to the front of the vehicle. Thus, as the vehicle is rotated, one side of the vehicle is raised above the other side of the vehicle. The vehicle rotation also causes the weight of the vehicle to shift away from the raised tires towards the lower tires as the angle of rotation increases. Because the roll characteristics of a vehicle change when the vehicle is loaded with different cargos, designers typically perform a number of roll tests on each new vehicle to represent several different cargo possibilities.
A number of important roll characteristics can be calculated from the data that is gathered from roll testing a vehicle. One characteristic is the rollover point of the vehicle. The rollover point occurs when the weight of the tires fully shifts away from the raised tires onto the lower tires, thus representing the point at which the vehicle may fall over onto its side. Therefore, the rollover point is an important safety characteristic in vehicle design. A number of other characteristics can also be determined from the roll test, including vehicle center of gravity, roll stiffness, lateral stiffness, torsional stiffness, and load shift between axles. A brief description of each of these characteristics will be helpful. The center of gravity of the vehicle represents a longitudinal axis through the vehicle around which the vehicle theoretically would freely rotate. This characteristic influences the angle of rotation of the rollover point and is useful in a number of other engineering calculations. Roll stiffness, or body roll, is a measurement of the angle of rotation of the vehicle body relative to the angle of rotation of the tires. Typically, the springs in the vehicle suspension contribute most to body roll. Lateral stiffness is a measurement of horizontal body movements parallel to the axles. This movement is usually caused by the suspension and is generally unwanted. Torsional stiffness is a specific measurement of the rotation of the vehicle frame during vehicle rotation. Typically, this characteristic is measured by attaching inclinometers along the length of the frame and comparing the differences in angular rotation between each of the inclinometers. Load shift between axles usually occurs between axles that share a linked suspension. Because the suspension components of a linked suspension are connected to more than one axle, a certain amount of weight may be transferred from one axle to another axle during vehicle rotation.
One problem often encountered in conducting roll tests involves gaining access to the facilities necessary to perform the tests. Traditionally, only independent laboratories have had facilities capable of performing the desired roll tests. In the case of heavy-duty vehicles, such as trucks and tractor-trailer rigs, only a small number of independent laboratories have had adequate facilities for conducting these tests. This situation has made scheduling the tests difficult because independent laboratories require a significant amount of planning notice to schedule each of their customers. Problems can also arise once the tests have started when unexpected complications occur that require more time than the laboratory has allotted. An additional problem involved with using independent laboratories to conduct roll tests is the high cost associated with the tests. Typically, the independent laboratories are operated as for-profit businesses. Thus, the vehicle designer must pay expensive fees for each of the tests that are conducted. In addition to the laboratory fees, however, the vehicle designer must also absorb extra costs associated with transportation to the laboratory, including the test vehicle, additional test equipment that may not be available at the laboratory, and the vehicle designer""s own technicians and engineers.
Another problem with using independent laboratories is the potential risk of disclosing confidential information related to the newly designed vehicles. Typically, the need for confidentiality during roll testing is particularly important because these test are usually conducted on new vehicle designs that the designer wishes to conceal from competitors and the marketplace. Thus, unintended disclosures before the product launch of the new vehicle may adversely affect the market for the designer""s new vehicle. Accordingly, independent laboratories are often viewed by vehicle designers as an area of potential risk for unwanted disclosures related to new vehicle. One potential area of risk for disclosures occurs when the vehicle is transported to the independent laboratory. Still another risk area occurs at the laboratory itself. As explained previously, independent laboratories usually serve many different customers at the same facilities. Thus, it is difficult for the laboratories to assure the same level of security that vehicle designers are accustomed to at their own facilities. Moreover, the testing facilities for large, heavy-duty vehicles are usually located outdoors with only minimal security provided.
The current equipment that independent laboratories use for roll testing generally is not adaptable for use by vehicle designers at their own design facilities. One problem with the current equipment is that it is usually permanently installed, and therefore, the space allotted for the equipment can only be used for performing roll tests. The total space required for roll testing equipment is often about twice the size of the vehicle being tested. Thus, in the case of large, heavy-duty trucks, the space required for roll testing equipment can be costly, especially if an indoor testing facility is desired.
Another problem with current test equipment is the high cost to build the equipment. One significant cost of these systems is the high performance hydraulic cylinders that are needed to lift and roll the test vehicle. In addition, a separate hydraulic power source to actuate the cylinders is usually needed. Typically, the hydraulic cylinder and the power source are specially purchased for the test equipment. The cylinders and power source are also usually permanently mounted in the equipment, making it infeasible to use this equipment for additional tasks.
Accordingly, a tilt platform is provided for roll testing an automotive vehicle. The tilt platform can be used with a standard floor hoist that is usually used for maintenance of automotive vehicles, thus providing a less expensive alternative to current test equipment. Support platforms can also be detached from the floor hoists, thus allowing the workspace and the floor hoists to be used for additional tasks.
The tilt platform includes a support platform that is pivotally attached to a floor hoist with a pivot pin. The pivot pin is positioned away from the midpoint of the support platform, thus forming a distal end and a proximal end of the support platform. Rollers are provided on the distal end of the support platform to enable the distal end to roll along a floor as the floor hoist is raised or lowered. The support platform also includes top support pads for supporting the weight of the vehicle tires.